1. Field
The present disclosure relates to a universal burn-in ball grid array socket, and more particularly, a top loaded burn-in socket which eliminates the need for hold down devices when the ball grid array package is inserted into the subject socket.
2. Description of the Related Art
Integrated circuits are typically housed within a package which is designed to protect the integrated circuit from damage, provide adequate heat dissipation during operation, and provide electrical connection between the integrated circuit and the leads of a printed circuit board. Several conventional packages are in the prior art including land grid array (LGA), pin grid array (PGA), ball grid array (BGA), column grid array (CGA) and quad flat pack (QFP).
Referring to FIG. 1A, a ball grid array (BGA) package 102 typically consists of a semi-conductor device 104 and a plurality of conductive ball leads 106 extending downwardly from the bottom surface 108 of the semi-conductor device 104. The BGAs generally place conductive ball leads over an entire surface of a chip, instead of just around the edges. Thus, BGA packages allow system designers to place more leads in a given package size using looser tolerances than peripheral lead type packages such as the quad flat pack (QFP). Therefore, board producers are not required to use the fine pitch spacings that are now necessary for high lead count packages. Also, BGAs have finer pitch spacings than pin grid arrays (PGA), since the solder balls do not have the coplanarality problem associated with through-hole PGAs.
In the prior art, the electrical connection between the BGA package and underlying printed circuit board (PCB), or electrical component, was generally provided by soldering the ball leads which are located underneath the BGA package onto pads which are provided on the upper surface of printed circuit boards.
In many applications, the soldering of the ball leads of the ball grid array package to the printed circuit board is undesirable. For example, it is impossible to visually locate a short or ground between the ball grid array package and printed circuit board. Usually, an expensive X-ray technique is required to inspect the connections since the ball leads are hidden under the ball grid array package. Further, the increasing number of ball leads being provided by ball grid array packages makes the soldering of the ball grid array packages to printed circuit boards more difficult.
Accordingly, in the prior art and disclosed in various patent publications, connectors have been developed which are designed to eliminate the need for the soldering the ball leads of a BGA package to a printed circuit board. More particularly, applicant is the inventor of U.S. Pat. No. 5,887,344 entitled “Method of Mounting a Plurality of Ball Leads onto a BGA Socket” which issued on Mar. 30, 1999 and is assigned to the assignee of the subject patent application. Applicant is also the inventor of U.S. Pat. No. 5,730,606 which issued on Mar. 24, 1998 and is entitled “Universal Production Ball Grid Array Socket”. U.S. Pat. No. 5,887,344 is a divisional application of U.S. Pat. No. 5,730,606. In turn, applicant is also the inventor of U.S. Pat. No. 5,984,694 which issued on Nov. 16, 1999 and is entitled “Universal Production Ball Grid Array Socket”, and said patent is a divisional application of U.S. Pat. No. 5,887,344. Applicant is also the inventor of U.S. Pat. No. 6,045,416 which issued on Apr. 4, 2000 and is entitled “Universal Production Ball Grid Array Socket”, and this patent is a continuation-in-part of U.S. Pat. No. 5,730,606. All of the above-mentioned patents are assigned to the assignee of the subject patent application. U.S. Pat. Nos. 5,730,606; 5,887,344; 5,984,694 and 6,045,416 are all incorporated herein by reference.
One of the possible shortcomings associated with prior art burn-in sockets is the requirement to have, as part of the socket, a means for holding down the chip scale package (CSP) or ball grid array (BGA) package in the socket, because of the spring forces acting to bias the respective package out of the socket. Such hold down means usually incorporates a plurality of individual pieces, in order to lock the ball grid array package to the socket. The additional locking means adds cost, as well as possible mechanical problems in connection with the mounting of a ball grid array package to a burn-in socket of the prior art type.
One example of a prior art type burn-in socket employs a spring pogo “Z” axis type of contact 110 which pushes up against the solder balls 106 of the BGA package as shown in FIG. 1B. Because of the spring structure of the pogo contact 110, the package 102 requires an opposite and reactive force to maintain contact between the pogo sockets and balls. The reactive force is provided by a hold down means which adds parts and complexity to the socket. Similarly, a spring type contact 112 shown in FIG. 1C results in the same disadvantages.
In another type of device as illustrated in FIG. 1D, stamped pins 114 are provided in the socket with a force directed in the “Z” axis direction, and again a hold down means must be provided for maintaining the ball grid array package in the burn-in socket of this prior art type.
A still further type of a prior art socket is shown in FIG. 1E. This type of socket uses dual pinch pins 116, and that type of contact also requires a hold down mechanism that adds parts and complexity to the burn-in socket. Furthermore, since the pinch pins engage a lower portion of the solder balls 106, damage may result to the solder balls.
Furthermore, another one of the possible shortcomings associated with prior art CSP/BGA production sockets is the possible wicking of the fluid materials used during the bonding of the ball leads onto an underside of a ball grid array socket. More particularly, it is important that the contact which extends through a hole in the substrate is tightly supported in the hole so as to ensure that no wicking of fluid materials takes place.
Accordingly, it is an object of the present disclosure to provide a top loaded, burn-in socket which does not require a hold down mechanism as part of the socket.
It is a further object of the present disclosure to provide a top loaded, burn-in socket which inherently includes structure for maintaining the interengagement of the ball grid array package in the burn-in socket, and thereby obviates the requirement for a hold down mechanism as part of the socket.
It is still a further object of the present disclosure to provide a top loaded, burn-in socket which does not require a hold down mechanism as part thereof, thereby eliminating unnecessary structural components within the burn-in socket and reducing the complexity of the socket structure.
It is another object of the present disclosure to provide a contact for a CSP/BGA production socket which is mounted to the socket in a manner to prevent wicking of fluid materials used for bonding a solder ball to the socket.